Added shaders for order independent transparency sample

Author: SaschaWillems

shaders/slang/oit/color.slang

@@ -0,0 +1,75 @@
+/* Copyright (c) 2025, Sascha Willems
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ */
+
+#define MAX_FRAGMENT_COUNT 128
+
+struct VSOutput
+{
+	float4 Pos : SV_POSITION;
+};
+
+struct Node
+{
+    float4 color;
+    float depth;
+    uint next;
+};
+RWTexture2D<uint> headIndexImage;
+
+struct Particle
+{
+	float2 pos;
+	float2 vel;
+	float4 gradientPos;
+};
+RWStructuredBuffer<Node> nodes;
+
+[shader("vertex")]
+VSOutput vertexMain(uint VertexIndex: SV_VertexID)
+{
+    VSOutput output;
+    float2 UV = float2((VertexIndex << 1) & 2, VertexIndex & 2);
+    output.Pos = float4(UV * 2.0f - 1.0f, 0.0f, 1.0f);
+    return output;
+}
+
+[shader("fragment")]
+float4 fragmentMain(VSOutput input)
+{
+    Node fragments[MAX_FRAGMENT_COUNT];
+    int count = 0;
+
+    uint nodeIdx = headIndexImage[uint2(input.Pos.xy)].r;
+
+    while (nodeIdx != 0xffffffff && count < MAX_FRAGMENT_COUNT)
+    {
+        fragments[count] = nodes[nodeIdx];
+        nodeIdx = fragments[count].next;
+        ++count;
+    }
+    
+    // Do the insertion sort
+    for (uint i = 1; i < count; ++i)
+    {
+        Node insert = fragments[i];
+        uint j = i;
+        while (j > 0 && insert.depth > fragments[j - 1].depth)
+        {
+            fragments[j] = fragments[j-1];
+            --j;
+        }
+        fragments[j] = insert;
+    }
+
+    // Do blending
+    float4 color = float4(0.025, 0.025, 0.025, 1.0f);
+    for (uint f = 0; f < count; ++f)
+    {
+        color = lerp(color, fragments[f].color, fragments[f].color.a);
+    }
+
+    return color;
+}

shaders/slang/oit/geometry.slang

@@ -0,0 +1,75 @@
+/* Copyright (c) 2025, Sascha Willems
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ */
+
+struct VSInput
+{
+    float4 Pos : POSITION0;
+};
+
+struct VSOutput
+{
+	float4 Pos : SV_POSITION;
+};
+
+struct RenderPassUBO
+{
+    float4x4 projection;
+    float4x4 view;
+};
+ConstantBuffer<RenderPassUBO> renderPassUBO;
+
+struct GeometrySBO
+{
+    uint count;
+    uint maxNodeCount;
+};
+// Binding 0 : Position storage buffer
+RWStructuredBuffer<GeometrySBO> geometrySBO;
+
+struct Node
+{
+    float4 color;
+    float depth;
+    uint next;
+};
+RWTexture2D<uint> headIndexImage;
+
+RWStructuredBuffer<Node> nodes;
+
+struct PushConsts {
+    float4x4 model;
+    float4 color;
+};
+
+[shader("vertex")]
+VSOutput vertexMain(VSInput input, uniform PushConsts pushConsts)
+{
+    VSOutput output;
+    output.Pos = mul(renderPassUBO.projection, mul(renderPassUBO.view, mul(pushConsts.model, input.Pos)));
+    return output;
+}
+
+[shader("fragment")]
+[earlydepthstencil]
+void fragmentMain(VSOutput input, uniform PushConsts pushConsts)
+{
+    // Increase the node count
+    uint nodeIdx;
+    InterlockedAdd(geometrySBO[0].count, 1, nodeIdx);
+
+    // Check LinkedListSBO is full
+    if (nodeIdx < geometrySBO[0].maxNodeCount)
+    {
+        // Exchange new head index and previous head index
+        uint prevHeadIdx;
+        InterlockedExchange(headIndexImage[uint2(input.Pos.xy)], nodeIdx, prevHeadIdx);
+
+        // Store node data
+        nodes[nodeIdx].color = pushConsts.color;
+        nodes[nodeIdx].depth = input.Pos.z;
+        nodes[nodeIdx].next = prevHeadIdx;
+    }
+}